Recently circulatory diseases such as arterial sclerosis and aortic aneurysms have especially been increasing. In order to treat aortic aneurysms, surgical thoracolaparotomy has been applied. Recently, however, low-invasive transcutaneous treatments have been adopted in which various types of devices such as an artificial blood vessel, a stent, a stent graft or a balloon are inserted into and detained in an affected area through a catheter introduced into a body from a dissected arterial blood vessel.
When transcutaneous treatment is provided to an aortic aneurysm with the above-mentioned technique, there might be a case where a thrombus that has pooled in an affected area becomes alienated and flows into a blood vessel through an inner wall of a blood vessel that has become fragile. In this case, when the alienated thrombus travels by blood flow into a narrow peripheral blood vessel, there is a risk that tissue ahead of the thrombus will become necrotized.
Especially, a thrombus blocking an arteria carotis communis in the head is immediately life-threatening.
In order to avoid the above-mentioned risk, an alienated thrombus capture device, referred to as a filter device, has been developed that is arranged at a peripheral side of an affected area where a device such as an artificial blood vessel is detained, and to capture and receive a thrombus that becomes alienated in the blood vessel. This kind of device has the following arrangement: either an opening edge portion or a closed distal end portion of a bursiform portion made of a mesh material is fixed to distal end portion of a flexible transport wire that is inserted into a catheter, the bursiform portion is enclosed in the catheter in a shape along the transport wire in a narrowed state, such that when the bursiform portion is released from a distal end of the catheter together with a distal end portion of the transport wire at an appropriate position located at a peripheral side of the affected area, an opening edge portion of the bursiform portion is spread open. In addition, the transport wire is arranged to pass through a lumen of an artificial blood vessel, which is released from a sheath into which the catheter is inserted, to the affected area after or at the same time the bursiform portion is released. Further, after the artificial blood vessel is detained at the affected area, the opening edge portion of the bursiform portion is narrowed by pulling the transport wire into the catheter. With this condition kept, the alienated thrombus capture device in which the thrombus is enclosed in the bursiform portion is pulled out of the body, so as to be retrieved by pulling it into the sheath.
In the above-mentioned conventional alienated thrombus capture device, a flexible wire is bent into a loop, both ends are bound and fixed to the transport wire and an opening edge portion of a bursiform portion is mounted on the loop of the wire. In another arrangement of the conventional alienated thrombus capture device, multiple flexible wires are shaped as a spindle, both ends of the multiple flexible wires being fixed to two points separated in a longitudinal direction on the transport wire, an opening edge portion of a bursiform portion is mounted on an intermediate portion in a longitudinal direction of each wire, and a closed distal end portion of the bursiform portion is mounted on a distal end portion of the wire.
However, for the first mentioned conventional arrangement, wherein the looped wire is used, since the looped wire is supported at a single point by the transport wire, it is difficult to coincide a direction of a center axis of the bursiform portion with a direction of blood flow, and the alienated thrombus capture device might incline and fail to capture a thrombus. In addition, after an artificial blood vessel is detained at an affected area, an opening width of the loop is narrowed when the wire is pulled into the catheter; however, a width of an opening edge portion of the bursiform portion that is still open tends to be wide, and a thrombus that has been enclosed inside the bursiform portion might get out from the opening edge. In this kind of alienated thrombus capture device, a part of the looped wire is made thin or cut so that the looped wire can be folded smaller when retrieved; however, this makes no difference in the problem that the device itself inclines.
For the later mentioned conventional arrangement, the multiple wires in a shape of a spindle are used, since the arrangement is complicated and the wires are bulky, it becomes hard to enclose multiple wires in the catheter. In addition, it is difficult for the opening edge portion of the bursiform portion to take its form along the inner wall of the blood vessel, due to the existence of wires. Thus, a thrombus might pass through a gap between the opening edge portion and the inner wall of the blood vessel. In order to solve the above-mentioned problem, the shape of the opening edge portion should be close to a perfect circle, which requires more wires, thereby making the arrangement more complicated and more bulky.
Further, as a problem common to the conventional alienated thrombus capture devices, since the transport wire is passed inside the artificial blood vessel, the arrangement as a whole becomes complicated and the transport wire might be a hindrance by entwining with other wires used to transport or to detain the artificial blood vessel.